The present invention relates to a method of and arrangement for determining geohydraulic permeability of ground regions through which ground water flows, particularly for dimensioning a well providing a ground water circulation.
The determination of the geohydraulic permeability of ground regions is important for the dimensioning of wells which are produced in these ground regions. Depending on the degree of the permeability of the ground region, for example the depth and the diameter of the well shaft is determined as well as the selection of filter with which the well shaft is coated. It is especially important to provide the permeability determination for wells with a ground water circulation in the ground region which surrounds the well shaft. The range of the ground water circulation strongly depends on the geohydraulic permeability of the ground region as well as on its anisotrophy or in other words its different sizes and in different directions. Especially the ratio of the permeability in horizontal vertical direction to the permeability in the vertical flow direction is very important. Such wells providing a ground water circulation are utilized especially for removing contaminations in the ground region through which ground water flows. Only by the determination of the geohydraulic permeability of the contaminated ground region is it possible to preliminarily calculate how to dimension the well for covering the whole contaminated ground region and whether a second well is needed in some cases.
The geohydraulic permeability of ground has been determined by pumping tests. For this purpose wells are bored in the ground region to be investigated, and ground water is pumped out from them. By the pumping out, the ground water level in the surrounding area of the well shaft lowers. The degree of the lowering of the ground water level is determined by a level tube which is inserted in the ground at different distance from the well shaft. From the water quantity removed from the well shaft and the degree of lowering of the ground water level in the surrounding area of the well shaft the permeability of the ground can be determined. This known method has the disadvantage that it cannot be performed in cultivated areas since by the lowering of the ground water level also a lowering of the structures near the well shaft is possible. Moreover, since it is necessary to introduce level tubes in the surrounding area of the well shaft for measuring the lowering of the ground water level, the method is relatively expensive and requires a great measuring area. A further disadvantage is that the ground water withdrawn from the well shaft must be again supplied into the ground region. This must be performed at a certain distance from the well shaft for avoiding a falsification of the measuring results, which is very expensive.